1. Field of the Invention
The present invention relates to a structure allowing for detection of a load applied to a vehicle seat. In particular, the invention is directed to such load detection structure for use in a vehicle seat.
2. Description of Prior Art
Recent years have witnessed a tendency for various automatically controlled functions and mechanisms to be increasingly incorporated in vehicle or automobiles, including safety devices such as air bags for protecting passengers against a great impact automatically in response to a collision, as well as various kinds of seat position adjustment devices for automatically adjusting the positions of seat sensitive to driver""s or passenger""s physiques and seating conditions. With such automated control innovations, there have been also found technical improvements to a passenger detection system for detecting the presence and absence of a passenger or driver in a seat of vehicle in advance before actuating or stopping the associated mechanical elements to automatically control various functions and mechanisms built in the seat.
Normally, the passenger detection system employs various sensors (e.g. a pressure sensitive element) which detect the weight of a passenger on a seat and emit a signal to electronic control systems for automatic control of various mechanical elements related to the seat. Most of the sensors are of a simple structure which can only sense the presence and absence of passenger on a seat, but the recent high-tech control technology inevitably requires that the sensors should further detect whether the passenger is an adult or a child as with an air bag control system for instance.
To meet the demand, there have been proposed sensor systems for numerically detecting the weight of passenger or a corresponding load applied to the seat, determining whether the passenger is adult or child, according to a numerical data obtained, and then controlling and adjusting the associated mechanical elements to optimal conditions suited for the adult or child (e.g. controlling air bag), as disclosed from the Japanese Laid-Open Patent Publications Nos. 11-001153 and 11-304579. Namely, the Japanese Laid-Open Patent Publication No. 11-001153 shows a combination of an impact sensor and four load sensors, wherein each of the four load sensors is interposed between a slide rail device on which the seat is mounted and a support leg member fixed on the floor of vehicle. It also suggests an H-shaped base plate on which wiring of the load sensors is collectively arranged for electrical connection with another one cable. According thereto, the weight of an occupant on the seat is detected by the four load sensors in a collision case, and a signal emitted therefrom is determined by a control unit as to the numerical amount of the occupant""s weight, so that the air bag is adjusted in inflation according to the numerical data on the occupant""s weight, thereby realizing a proper inflation of air back to protect the occupant if optimally according to his or her physique. On the other hand, the Japanese Laid-Open Patent Publication. No. 11-304579 discloses plural link mechanisms each having an arm pivoted therein, the link mechanisms being arranged between a slide rail fixed to a seat and a support base fixed on the floor of vehicle. In this prior art, a load sensor is provided at the free end portion of each arm of the link mechanism, such that a load applied vertically to the seat is imparted through the pivoted arm as an amplified or reduced vertical motion to the load sensor which then detects the amount of such vertical motion and determine a total weight of the seat and occupant on the seat. This reference states that a signal corresponding to the total weight may be emitted from the load sensors to a control unit associated with air bag and seat adjustment device, for instance.
However, the Japanese Laid-Open Patent Publication No. 11-001153 has no description regarding the mechanical structure of load sensor itself, and has no specific teaching on how the load sensor structurally supports the seat and how it actions to detect the seat occupant""s weight. This prior art is therefore neither realistic nor practical in assembling an optimal mechanical structure between the sensor and seat. The Japanese Laid-Open Patent Publication No. 11-304579 is found defective in that its link mechanism and pivoted arm are complicated in structure and further they occupy much of space heightwise between the seat and slide rail device, which results in the seat becoming large vertically in size and increasing its weight. Consequently, there remains a room of improvement in materializing a simplified and effective structure for this sort of load detection system. Also, no particular design has been contemplated to make assembling the load detection system easy and to render the structure of load detection system adaptable for mounting on the shape and condition of floor of vehicle.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved load detection structure which is greatly simplified in structure with reduced number of constituent elements and effective in avoiding undesired increase in height of the seat.
In order to achieve such purpose, according to the present invention, there is basically provided a load detection structure arranged under a bottom side of seat cushion of a vehicle seat and in a support leg means having a pair of mutually opposed vertical walls, the load detection structure including a load detection means for detecting a load applied from a seat occupant to the vehicle seat, wherein the load detection means comprises:
a block member having an elongated body extending in the longitudinal direction thereof, the block member having a rigid yet elastically deformable property and including, defined therein, a securing portion, a pivotal end portion, and a thin intermediate portion between the securing portion and pivotal end portion,
a strain gauge means fixedly attached to the thin intermediate portion of block member;
opening means defined in the support leg means;
two holes formed respectively in the pair of mutually opposed vertical walls of support leg means;
a pin means provided in the securing portion of block member; the pin means including a small-diameter portion and a large-diameter portion, wherein the small-diameter portion is secured in the securing portion of block member, and the large-diameter portion extends downwardly through the opening means, with a small clearance given peripherally thereof to space the large-diameter portion from the opening means, wherein the large-diameter portion has a flat head large in diameter than the opening means;
a pair of flanged collars; and
the block member being interposed between the bottom side of the seat cushion and the support leg means in such a manner that the securing portion of block member is a securely connected with bottom side of seat cushion, while the pivotal end portion of block member is rotatably journalled via a pivot pin between the pair of mutually opposed vertical walls of support leg means by fitting the pair of flanged collars in the respective two holes and then inserting the pivot pin through those pair of flanged collars and two holes;
wherein, when a downward load is applied to the seat in a vertical direction, the securing portion of the block member is displaced in a generally rectilinear downward direction, while at the same time, the pivotal end portion of the block member is rotated about the pivot pin, whereupon a difference is caused in movement and direction between said securing portion and said pivotal end portion, thereby causing deflection of the thin intermediate portion, and, in response thereto, the strain gauge detects an amount of the deflection and emits a corresponding value indicative of an amount of the load.
Accordingly, there is eliminated the need to provide a great number of intricate parts and fittings for assembling the load detection structure in the seat as found in the prior art. It is therefore quite easy for a worker to assemble the seat with such load detection structure at highly reduced costs, and also, the worker can quickly secure the thus-assembled seat to the vehicle floor. The two flanged collars can easily be fitted in the respective two bearing holes and stably set therein temporarily, which makes it extremely easy for the worker to insert the pivot pin through both of the two holes and, thereby expediting the process for assembling a seat. For, this is indeed superior to the troublesome steps of interposing cylindrical spacers between the block member and support leg member while simultaneously inserting the pivot pin through all the bores and spacers. The flanged collars are also effective in preventing the block member against transversal dislocation with respect to the support leg means, thus contributing to a high sensitivity of the strain gauge to the vertically applied load or force.
In one aspect of the present invention, the pin means may comprise at least two pins, each being so formed to have the small-diameter and large-diameter portions, and the opening means may comprise a pair of spaced-apart holes formed in said bottom wall of the support leg means.
In another aspect of the present invention, the pin means may comprise one pin so formed to have the small-diameter and large-diameter portions, and the opening means may comprise one hole formed in the bottom wall of the support leg means.
Other various features and advantages of the invention will become apparent from reading of the descriptions hereinafter, with reference to the annexed drawings.